Published on 17.8.2022

Catchment areas for defining accessibility of schools

Children in all parts of the world should have the right to education, and many do. But in order for children to be able to actually use this right, there also needs to be a school within a reasonable distance. Here the schools’ physical locations play a pivotal role, and governments also have an obligation to place schools in locations where pupils can reach them in travel times adapted to their age, while at the same time ensuring safe and direct school routes. However, the lack of tools for analysing school accessibility has often proven to be a bottleneck.

Gispo has worked together with The International Institute for Educational Planning (IIEP), that is an arm of UNESCO, to improve the methodologies used for analysing school placement and accessibility. The final result of the collaboration project with UNESCO is a QGIS plugin called “the Catchment” developed and published by Gispo.

In order to make the needed analysis, ministries of education and local authorities can now use catchment areas. A traditional bird’s-eye view is not enough to estimate the reachability of a point due to its incapability to take enough terrain-related factors into account. For instance, a large hill or lack of roads between a home and a school would greatly affect the time needed to make the journey. Physical proximity requires the use of isochrones to determine the catchment areas, i.e. defining the area which is actually reachable from a single point within a given time. By using georeferenced data of population and school locations, it is possible to estimate and analyse whether or not a potential learner can be serviced by the education system within reasonable distance and how the situation could be improved where needed.

The Catchment plugin calculates isochrone-based geographical catchment areas and relies on a GraphHopper backend and OpenStreetMap data to perform the calculations. The user can select the parameters for calculation such as a desired point or a whole point layer, travel mode (walking, cycling, driving) and travel distance. The customisation of the plugin allows the user to choose how the results are presented. For example, the resulting isochrones will be individual units for each school by default but it is also possible to merge all the distance polygons.  It is also possible for users to add indoor walking distances like the time spent walking from the school entrance to the classroom since it can be a factor in big schools that have buildings in different locations for different classes.

The published IIEP paper includes case study examples, such as analyses done with school data provided by the Jamaican Ministry of Education, Youth, and Information. One analysis resulted in the following visualisation (Figure 1) that describes the travel times around Central Branch Infant School in Kingston, Jamaica. Given how topographically diverse Jamaica is, its characteristics served as an excellent example for a scenario where this analysis is useful.

accessibility of schools
Figure 1. Isochrones and straight-line buffer around Central Branch Infant School, Kingston, Jamaica.

The different colours in Figure 1 represent different ranges of time spent by a potential learner travelling between their home and the school whilst the black circle delineates the 5-km straight-line buffer around the school. The analysis shows that it is possible for a student to live within the 5-km radius even though some areas within the buffer might make it topographically, or in terms of road connectivity, impossible to travel to the desired school within a reasonable amount of time. In other words, there can be an illusion of services.

Going to school is still a daily challenge for many people and for that purpose the isochrone methodology can provide insightful and useful results that can be used for further analysis and planning. Thus, the Catchment plugin can be used especially to improve access to education, but also to estimate the potential number of students in schools, to optimise delivery routes or to calculate school inspection routes.

The source of the content in this post and the full UNESCO-IIEP and GISPO paper is available here.

More in depth take on the plugin and how it works can be found here.

Plugin is available in the QGIS plugins repository.

The QGIS plugin source code can be found on GitHub.


Anna Saarinen

Anna is a M.Sc. (geoinformatics) student who is interested especially in spatial data analysis and visualization. In her free time Anna's activities consist of music, literature, cooking and outdoor activities.